1. Field of the Invention
The present application is directed to flight control law architectures for unmanned and manned aircraft.
2. Description of Related Art
Conventional aircraft control designs generally include one or more of a feedback gain and logic design which are utilized to switch between control loops with switches and/or buttons. The logic design utilizes the classic logic tree so that the flight control computer (FCC) and vehicle management system (VMS) architecture will be effective for maneuvering flights. An autopilot design will then be implemented by the third party to make aircraft to fly all kinds of hold mode. This design is strictly limited to manned type of the flight control system. Unmanned and optionally manned types of flight cannot be conducted with this kind of design.
A common objective of semi-autonomous operation for the future vertical lift (FVL) of defense vertical take-off and landing aircraft (VTOL) has brought significant attention in recent years. It is believed that a conventional rotorcraft is no longer suitable for the future combat. As such, fly-by-wire (FBW) systems with high performances aircraft characteristics are key features for future defense and commercial VTOL helicopter fleets. For example, it has been found that a blend of manned and unmanned aircraft fleets can perform scout missions more effectively than that of piloted aircraft alone.
Vehicle management systems (VMS) and aircraft control laws (ACLAWS) play important roles in making various flight missions possible. A well designed VMS integrated with flight control computer including advanced flight control laws can simplify the most difficult and complicated tasks. With integration of VMS and flight control computer with control laws, the system should be appreciated that advanced flight control systems incorporate multiple control laws where each control law is tailored towards a particular flight condition. These systems need to respond to multiple forms of control inputs which include control stick, beep and guidance command inputs. These inputs come from either the pilot on-board for piloted aircraft or from a remote operator for Unmanned Aerial Vehicles (UAV).
Such systems also include various automatic modes, for example, waypoint guidance, automatic takeoff and landing, and others. The VMS integrates all these functionalities and subsystems together and receives various inputs such as sensor measurements, control positions, automatic mode selection, and so forth. With conventional systems, these inputs pass through multiple logic trees to determine flight conditions and the intended vehicle mode of operation by using switches or buttons inside the cockpit. The system decides the best control law for these conditions and sends commands to switch to the appropriate control law. When more functionalities and subsystems are added to VMS, the complexities to integrate these together will increase rapidly for future vertical lift. The methodologies to make the new complex systems easily integrated together as a basis for future updates is extremely important to accelerate rapid changes of this powerful autonomous machine.
A number of conventional VMS FCC systems utilize a logic tree architectural, which is restricted to using logic type for internal and external variables. These variables can be assigned only one of the two values: True or False. Sometimes these values are represented by numbers 0 and 1. This method requires using a sophisticated network of “AND”, “OR”, “NOT” logic blocks along with various types of Set-Reset latches. Thus, the conventional systems create a complex logic tree even for a simplistic analysis. Increasing complexity of the logic trees increases the number of internal variables, resulting in significant exhausted time spent during the analysis. Furthermore, the output variables can only turn on or turn off a control law based on their value of true or false, thus requiring at least one output variable for each control law implemented. The number of variables increases, which adds additional test and evaluation burden in the certification phase of the flight control system. Moreover, the increased complexity makes it very difficult to add new subsystems that seamlessly integrate with the existing subsystems.
Therefore, conventional systems that utilize logic tree based systems will increase the burdens on the size of software, software tests, correctly software implementation and generalized software re-use/re-cycle/modularization for the complex vehicle management systems. There is a need for a different approach that can simplify the logic system, reduce number of internal and output variables, and still provide a capability to easily add new functionalities and subsystems without undue modifications to the overall system.
Although the foregoing developments represent great strides in the area of control law systems, many shortcomings remain.
While the system and method of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the process of the present application as defined by the appended claims.